1. Field of Application
The present invention relates to a load drive control system having a control apparatus such as a vehicle ECU (Electronic Control Unit), and a drive apparatus which drives a load in response to a control signal that is produced from the control apparatus.
2. Description of Related Art
Types of ECU that are used in a motor vehicle include for example a body ECU, a door ECU, air conditioner ECU, etc., which control respectively different loads. For example in the case of the air conditioner ECU, this controls the cooling cycle by driving the compressor of an air conditioner unit, and also controls the driving of a blower motor which produces a flow of cooling air.
FIG. 5 is a simplified diagram of a prototype of a blower motor drive control system based on an air conditioner ECU 1. A blower motor (not shown in the drawing) is driven by a main circuit 3 of the drive apparatus 2. The output voltage of the vehicle battery is supplied as a DC power source to a waiting status control circuit 4. When the air conditioner is not being used, so that driving of the blower motor is not required, the waiting status control circuit 4 sets the operation of the main circuit 3 in a waiting status. The waiting status control circuit 4 establishes this waiting status in response to a command value VIN, determined by a control signal from the ECU 1 being at a specific potential. When the transistor 10 in the ECU 1 is set in the ON state, this constitutes the outputting of a waiting status release command, whereby the waiting status control circuit 4 sets the main circuit 3 in the operating condition. In that way, the main circuit 3 is selectively set in a waiting status or in an operating status, under the control of the command signal that is supplied from the ECU 1.
However with such a system, DC supply power must be continuously supplied from the vehicle battery to the waiting status control circuit 4 and to an internal DC power supply circuit 5A of the drive apparatus 2, even while the waiting status is established.
Thus, such a prototype system has the disadvantage that battery power must be continuously supplied to an internal DC power supply circuit of the drive apparatus 2 while the main circuit 3 is in the waiting status, i.e., while the drive apparatus 2 is not in use. At present, there is a requirement to reduce such forms of power consumption, as far as possible.